Synthetic target

3- Aminonocardicinic acid, 233 Ancepsenolide, 74 Antheridium-inducing factor, 259 Anthracyclines and derivatives, 71, 156, 

4-Demethoxydaunomycinone, 71 1-Deoxynojirimycin, 175 Dihydroactinidiolide, 77 Dihydrosphingosine, 31 25,28-Dihydroxy-7,8-dihydroergosterol, 151 Dodecahedrane, 251 (Z)-8-Dodecenyl-l-acetate, 281 

Helminthogermacrene, 304 Hirsutene, 153 Hirsutic acid, 117 26-Hydroxy cholesterol, 151 

Methoxatin, 29 a-Methyldopa, 250 Methylenomycin B, 177, 198 Methyl (Z)-jasmonate, 292 Mitomycins, 245 Muscone, 275 

Talaromycin A, 64 Terpenes, 113 Tetracyclin, 226 Trifluororetinals, 323 Triterpenes, 169 flr-Turmerone, 81, 144 Tylophorine, 330 

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In synthetic target molecules esters, lactones, amides, and lactams are the most common carboxylic acid derivatives. In order to synthesize them from carboxylic acids one has generally to produce an activated acid derivative, and an enormous variety of activating reagents is known, mostly developed for peptide syntheses (M. Bodanszky, 1976). In actual syntheses of complex esters and amides, however, only a small selection of these remedies is used, and we shall mention only generally applicable methods. The classic means of activating carboxyl groups arc the acyl azide method of Curtius and the acyl chloride method of Emil Fischer. 

Simple compounds are defined here in an unusual but practical way a simple molecule is one, that may be obtained by four or less synthetic reactions from inexpensive commercial compounds. We call a commercial compound inexpensive if it costs less or not much more than one German mark per gram. This also implies, that only those compounds that cannot be purchased inexpensively are considered as synthetic target molecules in this book. 

As was the case with reactions of vinylindoles, the most elaborate synthetic targets approached by the indole-2,3-quinodimethane route have been alka-loids[18]. The route has been applied to aspidospenna[l9 ] and kopsine[20] structures. The fundamental reaction pattern is illustrated in equation 16.7. An indole-2,3-quinodimethane is generated by W-acylation of an Ai-(pent-4-enyl)-imine of a 2-methyl-3-formylindole. Intramolecular 2 -P 4 cydoaddition then occurs. 

Antithetic Analysis. (Synonymous with Retrosynthetic Analysis) A problem-solving technique for transforming the structure of a synthetic target molecule to a sequence of progressively simpler structures along a pathway which ultimately leads to simple or commercially available starting materials for a chemical synthesis. 

The pentacyclic plant alkaloid camptothecin has been a popular synthetic target because of its antitumor activity. Retrosynthetic disconnection to tricyclic intermediate A and chiral lactone B followed from multistrategic planning. 

Owing to their frequent occurrence in natural products and their synthetic utility, 2(5//)-furanones are important synthetic targets and intermediates. In considering the methods for the preparation of these compounds, we will emphasize the recent developments in this area. 

Thiazoles are important heterocycles and continue to be interesting synthetic targets because several classes of annulated thiazoles and thiazolyl (hetero)arenes display a diverse array of biological activities. 

The choice of cydo-C z as a prime synthetic target was based on the evaluation of its chemical stability and on the availability of a suitable synthetic sequence [23]. In structure la, the bond angle at each sp-hybridized C atom is distorted from the ideal value, 180°, to -160°. This distortion requires about... 

Conversion of Xa to the Hydrlndan XIII. The ultimate synthetic target of these investigations is a mixture of the tricyclic alcohols XIV (Scheme II). In the Sih synthesis (3) the methyl ester... 

Production of all naturally occurring polymers in vivo is catalyzed by enzymes. Polymerizations catalyzed by an enzyme ( enzymatic polymerizations ) have received much attention as new methodology [6-11], since in recent years structural variation of synthetic targets on polymers has begun to develop highly selective polymerizations for the increasing demands in the production of various functional polymers in material science. So far, in vitro syntheses of not only biopolymers but also non-natural synthetic polymers through enzymatic catalysis have been achieved [6-11]. 

Weik and Rademann have described the use of phosphoranes as polymer-bound acylation equivalents [65]. The authors chose a norstatine isostere as a synthetic target and employed classical polymer-bound triphenylphosphine in their studies (Scheme 7.54). Initial alkylation of the polymer-supported reagent was achieved with bromoacetonitrile under microwave irradiation. Simple treatment with triethyl-amine transformed the polymer-bound phosphonium salt into the corresponding stable phosphorane, which could be efficiently coupled with various protected amino acids. In this acylation step, the exclusion of water was crucial. 

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